According to the isotropic requirements of micro-nano Coordinate Measuring Machines(CMMs) for a probe, four kinds of elastic structure design schemes for the probe were proposed. A three-dimensional stiffness model of elastic structure was established by mechanical analysis. The stiffnesses of four elastic structures were simulated by using finite element analysis software ANSYS, and the performance characteristics of the four structures were analyzed and discussed, In consideration of a variety of factors like measuring stiffnesses, sensitivity and stable compact structures, a cross shape structure was selected as the elastic structure of micro-nano CMM probe, and its structure parameters were optimized and stiffness isotropic was designed. A high precision three-dimensional micro displacement test platform was set, and the measuring range, linearity and displacement error of the probe were tested and verified by experiments. Simulation and experiment results show that the elastic structure of the probe meets the requirement of a measuring range of 40 μm×40 μm×20 μm, stiffness less than 0.5 mN/μm and stiffness isotropic, and its overall measurement error is less than 100 nm.